This invention relates to an ignition timing control apparatus for reducing the knocking generation of an engine, and particularly to an ignition timing control apparatus for controlling the ignition timing of each cylinder in order to reduce the knocking generation in a multi-cylinder engine.
For properly suppressing the generation of knocking (hereinafter, simply referred to as knock), there has been proposed a knock feedback system for example, in U.S. Pat. Nos. 4,120,272; 4,153,020; and 4,269,155 to keep optimum output of the engine with low fuel cost. The knock sensor used in this system is an acceleration sensor for detecting the knock vibration of the engine. As a method of suppressing the generation of knock by controlling the ignition timing upon knock generation, there has been proposed a system of independently controlling the ignition timing of each cylinder.
In the knock feedback system disclosed in the U.S. Patents mentioned above, since knock is detected from the vibration of the engine, the precision of knock detection is different at each cylinder and therefore knock detection for every cylinder cannot be made. Accordingly, the engine cannot be operated in order to achieve the optimum output at each cylinder. In the knock suppressing method of independently controlling ignition timing of each cylinder, there is a drawback that for example, in an 8 cylinder engine at least 8-time knock sound is generated in each of 8 cylinders because of the independent control, thus knock sound being very frequently caused.